Network Working Group H. Schulzrinne
Internet-Draft V. Singh
Intended status: Standards Track Columbia University
Expires: February 18, 2010 H. Tschofenig
Nokia Siemens Networks
M. Thomson
Andrew Corporation
August 17, 2009
Dynamic Extensions to the Presence Information Data Format LocationObject (PIDF-LO)draft-singh-geopriv-pidf-lo-dynamic-07
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Internet-Draft Dynamic Extensions to PIDF-LO August 20091. Introduction
The Presence Information Data Format - Location Object (PIDF-LO) (see
RFC 4119 [RFC4119]) provides geographical location of a presentity.
This corresponds to a physical location at a given instance of time.
With the extensions defined in [RFC5491] more guidelines to
implementers are being provided with respect to the expression
location information in PIDF-LO.
The addition of rate of change information to the PIDF-LO enables a
range of use cases. These use cases either directly use dynamic
information, or use that information for smoother tracking of a
position over time. For example, an application that continuously
tracks a presentity could use velocity information to extrapolate
positions in between times location information is measured. A
shipping company could directly use speed to monitor delivery truck
speed to ensure speed limits are observed.
2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119
[RFC2119].
3. Dynamic Elements
This document defines a new element, <Dynamic>, for the conveyance of
dynamic information.
Dynamic information MAY be included without any other location
information being present. When dynamic information is associated
with information about the instantaneous position of the presentity,
the <Dynamic> element MUST be included in the same <location-info>
element as the corresponding geodetic (or civic) location
information.
Dynamic information can be safely ignored by a recipient that does
not support this specification.
The <Dynamic> element contains the following components:
orientation:
The <orientation> element describes the spatial orientation of the
presentity; the direction that the object is pointing. For a
device, this orientation might depend on the type of device. See
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Internet-Draft Dynamic Extensions to PIDF-LO August 2009Section 3.1 for details.
speed:
Speed is the time rate of change in position of a presentity
without regard for direction; the scalar component of velocity.
The value for the <speed> element is a measure that is defined in
meters per second.
heading:
Heading is directional component of velocity. See Section 3.1 for
details.
acceleration:
Acceleration is the time rate of change of velocity. This element
contains the scalar component of velocity, measured in meters per
second per second.
Each element can be omitted if no information is available. In the
following example the presentity is approximately oriented to the
North at a slightly elevated angle. The presentity is travelling 24
meters per second to the West:
<?xml version="1.0" encoding="UTF-8"?>
<presence
xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:dyn="urn:ietf:params:xml:ns:pidf:dynamic"
xmlns:gml="http://www.opengis.net/gml"
entity="pres:alice@example.com">
<dm:device id="abc123">
<gp:geopriv>
<gp:location-info>
<dyn:Dynamic>
<dyn:orientation>-3 12</dyn:orientation>
<dyn:speed>24</dyn:speed>
<dyn:heading>278</dyn:heading>
</dyn:Dynamic>
</gp:location-info>
<gp:usage-rules/>
<method>gps</method>
</gp:geopriv>
<timestamp>2009-06-22T20:57:29Z</timestamp>
<dm:deviceID>mac:1234567890ab</dm:deviceID>
</dm:device>
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Internet-Draft Dynamic Extensions to PIDF-LO August 2009
</presence>
Another example shows a PIDF-LO document of the presentity
alice@example.com on a bike traveling 12 meters per second and with
an acceleration of 2 meters per second. Her position is indicated as
a circle. The values for speed and acceleration might be used by a
receiver to adjust the uncertainty over time.
<?xml version="1.0" encoding="UTF-8"?>
<presence
xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:dyn="urn:ietf:params:xml:ns:pidf:dynamic"
xmlns:gml="http://www.opengis.net/gml"
xmlns:gs="http://www.opengis.net/pidflo/1.0"
entity="pres:alice@example.com">
<dm:device id="abc123">
<gp:geopriv>
<gp:location-info>
<gs:Circle srsName="urn:ogc:def:crs:EPSG::4326">
<gml:pos>42.5463 -73.2512</gml:pos>
<gs:radius uom="urn:ogc:def:uom:EPSG::9001">
100
</gs:radius>
</gs:Circle>
<dyn:Dynamic>
<dyn:speed>12</dyn:speed>
<dyn:acceleration>2</dyn:acceleration>
</dyn:Dynamic>
</gp:location-info>
<gp:usage-rules/>
<method>gps</method>
</gp:geopriv>
<timestamp>2009-06-22T20:57:29Z</timestamp>
<dm:deviceID>mac:1234567890ab</dm:deviceID>
</dm:device>
</presence>
3.1. Angular Measures and Coordinate Reference Systems
[RFC5491] constrains the coordinate reference system (CRS) used in
PIDF-LO to World Geodetic System 1984 (WGS 84) using either the two-
dimensional (latitude, longitude) CRS identified by
"urn:ogc:def:crs:EPSG::4326" or the two-dimensional (latitude,
longitude, altitude) CRS identified by "urn:ogc:def:crs:EPSG::4979".
Dynamic locations similarly assume that either of these coordinate
reference systems are used.
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Internet-Draft Dynamic Extensions to PIDF-LO August 2009
The <orientation> and <heading> establish a direction. Both measures
contain one or two angular values that are expressed relative to the
current position of the presentity (see Appendix A). Angular
measures are expressed in degrees and values MAY be negative. If two
measures are present, the values MUST be separated by whitespace.
The first measure specifies the horizontal direction from the current
position of the presentity to a point that it either pointing towards
or travelling towards. Horizontal angles are measured from Northing
to Easting. Horizontal angles start from zero when pointing to or
travelling towards the North and increase towards the East.
The second measure, if present, specifies the vertical component of
this angle. This angle is the elevation from the local horizontal
plane. If the second angle value is omitted, the vertical component
is unknown and the speed measure MAY be assumed to only contain the
horizontal component of speed.
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